In my prior U.S. Pat. No. 4,157,772, there is disclosed an apparatus for dispensing liquor from a bottle to a hand-held nozzle for preparing or mixing a drink. A number of similar dispensing units have been proposed and utilized commercially incorporating a hand-held dispenser gun or nozzle having a plurality of buttons thereon for selecting the type of liquor to be dispensed and cooperating with a solenoid valve which operates a piston for directing liquor from a chamber to the dispensing gun. In such prior apparatus the solenoid core or plunger is moved in both directions for starting and stopping the dispensing of liquor from the apparatus. When the operator first presses a button on the dispensing gun liquid begins to flow as a piston is depressed by pressurized gas introduced into the apparatus, and liquid flow is terminated when the operator releases the button. Since a specific and predetermined amount of liquid is to be automatically dispensed, if the operator inadvertently releases the button before the piston has been completely depressed to displace the intended amount of liquor, a "short pour" or inadequate amount of liquor is dispensed. Other dispensing units, attempting to obviate such a disadvantage have utilized a system in which the solenoid plunger remains in the open or activated position to allow full measure dispensing until the piston has become fully depressed thereby displacing all of the liquid in the cylinder, and in such a fully depressed position actuates or trips a switch for terminating voltage to the solenoid. Such additional switching not only complicates the system but increases manufacturing and maintenance costs. It is to the elimination of these disadvantages that the improvement of the present invention is directed.